The present invention relates to combustors for gas turbine engines and, more particularly, to nozzle covers and combustion nozzles useful in combustors of gas turbine engines.
A large gas turbine engine may include a plurality of combustors arranged in a circle about other elements of the engine. Fuel and air are admitted into each combustor to produce a fuel-air mixture.
One type of combustor, of interest to the present invention, employs a combination of fuels such as, for example, two different gasses or a gas and an air-atomized liquid, fed to each nozzle. Such a combustor typically burns gas fuel during normal operation. Alternatively, a liquid fuel, atomized by a vigorous swirling supply of air, emitted from the nozzle, may be burned. Combinations of either or both fuels in varying proportions may be burned.
A nozzle cover, forming the upstream end of the combustor, includes manifolds therein for conveying fuel gas and air to the locations of all of the several nozzles in that nozzle cover. The nozzles are installed in the nozzle cover to mate air and fuel-gas passages in the nozzles with corresponding manifolds in the nozzle cover. Liquid fuel is connected directly to each appropriate nozzle.
A nozzle cover is conventionally fabricated by machining, welding and brazing together individual elements to form the required manifolds. Threaded annular walls are provided in a special insert for installation of the nozzles and for the interfacing with the supply of liquid fuel and the fuel gas and air in the manifolds. In one design, the nozzle cover is formed of seventeen separate brazed or welded parts.
A nozzle cover of a combustor is a large object measuring, for example, about 22 to 27 inches across. The limitations of brazing require substantial precision, so that abutting surfaces to be brazed are close enough together to permit brazing to be performed successfully.
The prior art insert includes three coaxial, coplanar, annular walls to which the nozzle parts are affixed by threads. The conventional design leaves little room for insertion of tools for forming the required threads on the annular walls.